Is it logged somewhere in the Netlify UI (we cannot find it) or how do we add some logging to our deployment code that display the IP Adress (we use Gatsby) ?
You could also make a DNS lookup to get that information but I don’t believe that would be any simpler or more reliable that the solution you are using now. I recommend using your method above.
There is also an Enterprise plan feature that provides static IP addresses for the build system but that is a paid feature on Enterprise plans only: